1. Field of Invention
The present invention relates to an inverter, and more particularly relates to an inverter having one switching device.
2. Description of Related Art
With the rapid development in technology, flat panel displays (FPD) with their advantages of high image quality, compact size, light weight, low driving voltage and low power consumption have become very popular for incorporation into electrical devices and have become the mainstream display apparatus. For example, the FPD can be implemented in portable TVs, mobile phones, video recorders, computer monitors, and many other kinds of consumer electronics.
In the FPD, the backlight module is used as the light source. An inverter in the backlight module is used to drive several cold cathode fluorescent lamps (CCFL), and to adjust the brightness of these CCFLs. FIG. 1 is a circuit diagram depicting an inverter of the prior art. The inverter 110 of the prior art comprises a capacitor 114, several switching devices 116a, 116b, 116c and 116d, a driving circuit 140 and a transformer 150. A power source 130 is connected to the capacitor 114 via the switching devices 116a, 116b, 116c and 116d. The switching devices 116a, 116b, 116c and 116d are individually connected to the driving circuit 140, wherein the driving circuit 140 is arranged to control the switching devices 116a, 116b, 116c and 116d to turn on or turn off. Furthermore, the capacitor 114 and the switching devices are individually connected to the two terminals of the primary side 119 of the transformer 150. The capacitor 165 is connected between a terminal of a secondary side 160 of the transformer 150 and a cold cathode fluorescent lamp (CCFL). Therefore, the inverter 110 transforms a direct current of the power source 130 into an alternating current, and thus lights up the cold cathode fluorescent lamp 170 connected to the secondary side 160 of the transformer 150, wherein the cold cathode fluorescent lamp 170 can be used as the light source of the display panel 180.
No matter if the inverter of FIG. 1 is full bridge or half bridge (not shown); it needs more than one switching device. Thus, the chip will be bigger and more complicated when using more switching devices. Therefore, an inverter with less switching devices can reduce the size of the chip and simplify the design of the driving circuit.